In the last few years, particularly in the professional lighting channel, most conventional spot lamps have been replaced by Light Emitting Diode (LED) retrofit spot lamps because of the energy saving and short payback time. The difference in characteristics of the traditional incandescent light emitters and the LEDs require a different design of the optics, the heat management solutions and the electrical circuitry. Although different aspects must be designed differently, it is also required that a LED retrofit spot lamp can directly replace the traditional lamp without any modification to the luminaire. As such it is advantageous if a LED retrofit spot lamp has exactly the same shape and size as the traditional lamp.
For instance, JP 2011 198659 A discloses an LED lamp equipped with a light guide lens to guide the light from an LED light source, an incident face, an inside reflecting face, an outside reflecting face, and an emitting face are installed at the light guide lens. The inside reflecting face is formed by rotating a quarter arc around the center axial line arranged so that a tangent line to pass through the end point becomes parallel with the center axial line, so that the tangent line to pass through the end point becomes perpendicular to the center axial line, and so that the end point is positioned closer to the center axial line than the end point. The outside reflecting face is formed by rotating a quarter arc around the center axial line arranged so that the tangent line to pass through the end point becomes parallel with the center axial line, so that the tangent line to pass through the end point becomes perpendicular to the center axial line, and so that the end point is positioned closer to the center axial line than the end point.
For instance, US 2014/340927 discloses a lightguide which functions as a luminaire. The luminaire includes at least one solid state light source, such as an LED, and a lightguide configured to receive light from the solid state light source. Light from the light source is coupled into the lightguide and transported within it by total internal reflection until the light exits the lightguide. A shape of the lightguide causes and directs extraction of the light, and can also be used to create a particular pattern of the extracted light. Such shapes include linear wedges and twisted wedges. Optical films can be included on the light input and output surfaces of the lightguide.
For instance, WO 2014/080771 A1 discloses an illumination device which guides and projects projected light of LED elements via light guiding bodies which are configured from upper part light guiding bodies, middle part light guiding bodies, and lower part light guiding bodies. The upper part light guiding bodies are hollow cylinders, and the LED elements which project illumination light toward the partition wall inner parts of the upper part light guiding bodies are positioned on the upper end faces thereof. The middle light guiding bodies have flaring hollow shapes which are bent such that the illumination light which is projected and proceeds nearly linearly from the LED elements along the partition wall inner parts of the upper part light guiding bodies is blocked, and to widen in the outer circumference direction of the upper part light guiding bodies. The lower part light guiding bodies have hollow flange shapes extending in a nearly horizontal direction so as to be orthogonal to the upper part light guiding bodies.
For instance, US 2013/155719 A1 discloses a lightguide functioning as a luminaire. The luminaire includes at least one solid state light source, such as an LED, and a lightguide configured to receive light from the solid state light source. Light from the light source is coupled into the lightguide and transported within it by total internal reflection until the light exits the lightguide. A shape of the lightguide causes and directs extraction of the light. The shape can also be used to create a particular pattern of the extracted light.
An example of a spotlight based on Light Emitting Diodes is, for example, disclosed in CN204083872U. At a center of a reflector is provided a Light Emitting Diode and a light guide provided on top of the Light Emitting Diode. The emitted light is coupled into the light guide and because of the specific shape of the light guide a significant part of the light is emitted towards the reflector via side surfaces of the light guide. The reflector reflects the impinging light towards a light exit window or a light exit diaphragm of the spotlight such that a light beam is emitted into the surroundings of the spotlight. In such a solution the light guide is used to, and designed to, simulate the light emission pattern of a traditional incandescent light emitter. A similar solution is provided in JP5437128B2.
The solution of the above cited documents is difficult to integrate in, for example, an AR111 spot lamps. The specific design of the light guide of these document make the spotlight of the above cited documents relatively thick. Furthermore, it is about impossible to use the solution of the above cited document in an AR111 spot lamp if the AR111 spot lamp has to emit a relatively narrow light beam, e.g. with a Full Width Half Maximum (FWHM) beam angle of 7 degrees.